This invention relates to electrochromic structures, such as the exterior windows of a building, and panels, such as interior partitions in a building. The present invention is also applicable to other uses, as for example, to windows and/or panels in automotive vehicles as well as various other structures and/or devices employing windows and/or panels. More particularly, the present invention relates to electrochromic structures such as windows and panels wherein changes in the color of an electrochromic medium incorporated therein may be either enhanced or hidden when viewed from a predetermined direction, and wherein changes in the light transmission of an electrochromic medium incorporated therein may provide for differential privacy when viewed from similarly well lit opposing sides of the electrochromic structure.
Heretofore, partially light transmitting mirrors, sometimes referred to as one-way mirrors, have been devised wherein privacy may be obtained by employing differential light levels on opposing sides of a partially light transmitting reflectively coated window. Another prior technology used for privacy purposes is a polymer dispersed liquid crystal window which scatters light so as to provide for privacy. With still other prior technologies, variable transmittance electro-optic windows were devised which reduced the visibility through a window by lowering the transmission of light through an electro-optic medium, the level of privacy, herein defined as the ratio of reflectance to transmittance, being approximately equal when viewing from either side of the window in equal lighting situations. A low transmission, less than or equal to 5%, is required to obtain reasonable levels of privacy with this type of electro-optic device for lighting levels common to most buildings. Typically it is more expensive and more difficult to produce an electro-optic device with lower light transmission in the darkened state. Also, it is sometimes desirable to have a higher level of privacy from one side of an electro-optic window than from the other side thereof. This can not be achieved with prior variable transmittance electro-optic devices.
Heretofore, various electrochromic devices have also been proposed wherein the transmission of light therethrough or reflected thereby varies as a function of changes in light absorption of an electrochromic medium incorporated therein, the light absorption of the electrochromic medium, in turn, varying in response to the application of electrical potential to the electrochromic medium. Thus, devices of reversibly variable transmittance have been proposed for such applications as light filters, variable reflectance mirrors and display devices. The variable transmittance light filters have included windows and panels wherein the transmittance or reflectance of light is varied by thermochromic, photochromic, or electro-optic means such as liquid crystals, dipolar suspension, electrophoretic and electrochromic means, either solution phase or solid state or hybrid, and wherein the variable transmittance characteristics are present in at least the visible light spectrum, i.e. light wave lengths from about 3,800 angstroms to about 7,600 angstroms. Proposed control systems for variable transmittance windows and panels typically either permit the light transmittance of the windows and panels to be manually controlled through the application of electrical potential to an electro-optic medium to darken the windows and panels or the windows and panels may be automatically darkened through the agency, for example, of photocells or photovoltaic devices or other devices, which function to effect the application of electrical potential to the electro-optic medium. Numerous prior electrochromic devices are identified in U.S. Pat. No. 5,805,330, issued Sep. 8, 1998, and entitled Electro-optic Window Incorporating a Discrete Photovoltaic Device. U.S. Pat. No. 5,805,330 is owned by the assignee of the present invention and U.S. Pat. No. 5,805,330 is hereby incorporated herein in its entirety by reference.
In accordance with the present invention, electrochromic structures, such as windows and panels, are provided wherein differential privacy may be enhanced when viewed from a predetermined direction or wherein changes in the color of an electrochromic medium incorporated therein may be either enhanced or hidden when viewed from a predetermined direction, as for example, when viewed from the outside of a building or when viewed from one side of a transparent interior partition in a building.
The present invention is applicable, for example, to windows on the outside of a building and is also applicable to transparent panels or partitions in the interior of a building, as for example, transparent partitions or panels which define a room and which partitions or panels may be darkened, as desired, for privacy purposes. Thus, in accordance with the present invention, privacy may be enhanced on one side of an electrochromic structure by raising the reflectance on one of the surfaces of the opposing substrate incorporated in the window or panel. In addition, partially light reflective coatings may be incorporated in the windows or panels in a predetermined manner whereby any changes of appearance of a building due to changes in color of the electrochromic medium, when viewed from the outside of a building, may be hidden, or; in the alternative, partially light reflective coatings may be incorporated in the windows or panels in a predetermined manner whereby changes in appearance of a building, due to changes in color of the electrochromic medium, may be enhanced when viewed from outside the building.
Accordingly, an object of the present invention is to provide improved electrochromic structures, such as electrochromic windows and panels, which incorporate improved means for varying the amount of light that is transmitted therethrough and wherein privacy may be enhanced by raising the reflectance characteristics of one substrate relative to another substrate incorporated in the electrochromic structure.
Another object of the present invention is to overcome disadvantages in prior electro-optic structures of the indicated character, and to provide improved electrochromic structures wherein changes in the apparent color thereof may be either enhanced or hidden when viewed from a predetermined direction.
Another object of the present invention is to provide improved electrochromic windows and panels in which the transmittance of light therethrough or the reflectance of light thereby may be manually or automatically controlled to achieve an aesthetically pleasing appearance, or functional, i.e. displaying a pattern or wording on a building""s exterior.
Another object of the present invention is to provide improved electrochromic windows and panels incorporating improved means for providing a higher level of privacy, the ratio of light reflectance to light transmittance, than variable transmittance electro-optic windows and panels known in the prior art.
Another object of the present invention is to provide improved electrochromic windows and panels which enable the use of a partially light reflective and a partially light transmissive component as an electrode for the electrochromic medium.
Another object of the present invention is to provide improved electrochromic windows and panels which provide for a different level of privacy when viewing the windows and panels from one direction as compared to another direction.
The above as well as other objects and advantages of the present invention will become apparent from the following description, the appended claims, and the accompanying drawings.